In the fast-paced evolution of light-emitting diode (“LED”) package designs targeting cost reduction and reduced form factor, the development of chip-scale packages (“CSP”), which are flip-chip bonded LED die with exposed PN junctions at the bottom of the packages and light emission through a 5-sided silicon phosphor coating, is getting more popular.
Traditional LED device handlers need to pick up the LED units from a wafer frame, inspect, align, and then place these LED units onto a carrier tape. During such processes, it is necessary to avoid mechanical pressure on the LED unit causing deformation of the silicon phosphor, which would potentially affect its optical properties. It is also necessary to avoid placement of an LED unit onto an alignment module during orientation, which would risk scratching a bottom surface of the LED unit and damage the exposed PN junction. Thus, multiple pick arms on a turret with each pick arm having independent rotary capability is advantageous for correcting an angular alignment of the LED units without extraneous mechanical contact.
Existing designs adopt different approaches to avoid damage to the LED units. One approach is to use a slip ring module to transfer electrical signals and power to control multiple motor channels through physical conductive contact. However, there is an adverse effect of a shortened lifetime of the slip ring module due to friction during operation, and the slip ring module is also hard to replace. Another approach uses the engagement and disengagement of a motor with a gear to orientate an LED unit. After optical inspection to check the x, y, and theta positional shifts of an LED unit held on a pick arm, the turret arm would index to the next station that has a gear and a motor to engage the pick arm in order to correct the theta position of the LED unit. However, this approach can seriously slow down the machine's throughput.
It would be beneficial to introduce a wireless transmission system which helps to avoid the aforesaid shortcomings of the prior art approaches.